The driving assistance for a vehicle is exemplified by the detection of an obstacle in the traveling direction of the vehicle to issue a warning if it is feared that the vehicle may collide with the obstacle (see, for example, Patent Document 1). In this technique, the obstacle, which exists in the traveling direction of the vehicle, is detected by a radar. An approximate straight line, which indicates the movement locus of the obstacle, is calculated from the position information of the obstacle with respect to the vehicle. Thus, the presence of the obstacle is recognized. If the relative relationship between the approximate straight line and the vehicle meets a certain condition, then it is regarded that there is a fear of collision between the obstacle and the vehicle, and a warning is issued.